【作者】 曹士英；

【导师】 张志刚；

【作者基本信息】 天津大学 ， 光学工程， 2007， 博士

【摘要】 周期量级激光脉冲不仅是飞秒激光脉冲发展的必然趋势,也是产生阿秒脉冲、推动阿秒科学发展的必经阶段和必要手段。本论文主要围绕周期量级光脉冲获取的单元技术以及重复频率为100kHz的Yb:YAG薄片激光器两方面进行实验研究。论文的主要内容包括:一、将充气空心光纤技术与成丝技术相结合,实验分析了自由成丝状态和有空心光纤束缚成丝状态下的光谱差别,并系统研究了在自由成丝状态下,输入脉冲能量、充气气压对成丝光谱展宽的影响,以及有空心光纤束缚时,输入脉冲能量、空心光纤所处成丝位置、空心光纤芯径等实验参数对光谱展宽的影响。二、利用空心光纤作为探测器,在强飞秒激光在氩气中成丝的条件下,研究了成丝不同部位的光谱变化,进而推断出成丝范围内脉冲的时域变化。结果表明,空心光纤位于成丝的特定位置时可以获得最宽光谱展宽,对应于成丝部位的最窄脉冲,因此间接证明了成丝的长度范围内,脉冲宽度呈非均匀分布。三、对用于评价周期量级光脉冲时域信息的SPIDER装置进行了改进和完善,并成功推出了用于测量飞秒脉冲位相的硬件和软件系统,实现了可靠性、实用性的飞秒脉冲位相测量仪国产化机型。飞秒脉冲位相测量仪在硬件上,采用超薄、超宽带分束镜和超薄非线性转换晶体,有效地减小了附加色散并增大了测量带宽;在软件上,采用独立开发的新型解析算法使位相测量更加精确;在操作上,基于VC编程环境,开发出了具有美观友好的人机对话交互界面,使脉冲位相测量的操作更加可视化。四、利用薄片Yb:YAG晶体模块,实验分析了影响Yb:YAG薄片激光器腔内损耗的各种因素;采用声光调Q技术,分析了输出耦合镜透射率、偏振以及重复频率对调Q脉冲输出功率的影响,研究了影响Yb:YAG薄片激光器的调Q输出稳定性的因素,并进一步采用倍频技术获取了二倍频光脉冲输出。通过优化声光Q开关超声功率、Q开关开门宽度以及偏振性提高了脉冲输出的稳定性。在重复频率为100kHz的条件下,获得了平均功率50W的基频调Q脉冲输出,脉冲宽度205ns,脉冲不稳定性为2.0%rms以及20W的倍频光输出,脉冲宽度195ns,脉冲不稳定性为1.5%rms。为建立并实现100kHz的钛宝石激光放大器的提供了基础。更多还原

【Abstract】 Monocycle pulses are not only the inevitable trend of the development of femtosecond pulses, but also the necessary method and stage for the generation of attosecond pulse and the advancement of attosecond technology. In this dissertation, the unit technique of monocycle pulses, including filamentation, gas-filled hollow fiber and SPIDER, and a 100-kHz Q-switched Yb: YAG thin disk laser was experimentally investigated. The main contents are summarized as follows:1. Using the techniques of filamentation and gas-filled hollow fiber, the characteristics of the broadened spectrum formed by filament with and without the hollow fiber restriction are experimentally studied respectively when intense femtosecond pulses are focused into an argon-filled tube. The influence of the input pulse energy and the gas pressure on the broaden spectrum without the hollow fiber restriction and that of input pulse energy, the position and the inner diameter of the hollow fiber on the broaden spectrum with the hollow fiber restriction are also analyzed in detail.2. The spectrum evolution along the filament formed by the femtosecond laser in argon gas is experimentally demonstrated through introducing a hollow fiber as a probe. Using the spectrum variation, the time domain variation of pulses in the range of filamentaion can be concluded. At a particular position of the filament, the width of the spectrum expands to its maximum value, which corresponds to the shortest pulse duration. The results indicate that the width of pulses present a non-uniform distribution in the range of the filament.3. SPIDER apparatus which is used to evaluate the time domain information of monocycle pulses are greatly improved in the technological operation. And a set of SPIDER apparatus with hardware and software have been produced successfully. This domestic experimental equipment can realize measuring the phase of femtosecond pulses reliably and practicably. In the hardware of the SPIDER apparatus, ultrathin beam splitters with ultrabroad bandwidth film coating and the ultrathin nonlinear crystal are applied to reduce the additional dispersion and enlarge the measurement bandwidth. In the software, the novel arithmetic is used to ensure the precise measurement results. In the manipulation, based on the VC program, the beautiful and friendly interface is designed to make the measurement more visual. 4. Using the Yb: YAG thin disk modular, the influencing factors on the intracavity loss in a Yb: YAG thin disk laser is experimentally studied. Adopting the technique of acousto-optic modulation, the influence of the output coupler transmission, the polarization and the repetition rate on the acoustic-optic Q-switched output power is discussed respectively. The stability of the acoustic-optic Q-switched pulse is also experimentally studied. Based on the Q-switched thin disk laser, second harmonic generation is obtained by introducing a frequency doubling crystal. By optimizing the polarization, the driver power and the gate width of the AO device, the stability of the Q-switched pulses can be improved greatly. At the repetition rate of 100 kHz, the average fundamental power of 50W with 205ns pulse duration and 2.0%rms pulse stability can be achieved and the average frequency doubling power of 20W with 195ns pulse duration and 1.5%rms pulse stability can be gained, which will be helpful to constructing a 100 kHz Ti: Sapphire amplifier.更多还原